LERMA UMR8112

Laboratoire d’Études du Rayonnement et de la Matière en Astrophysique et Atmosphères



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Administrative team

by Carine Bingan - published on , updated on

The administrative team of LERMA is composed of 7 agents who work closely with the administrative services of the CNRS (Ile de France-Meudon delegation (DR5) and INSU), the Paris Observatory (OP), the Sorbonne University (SU) and the University of Cergy Pontoise ( UCP). LERMA’s administrative team supports research activities by ensuring the administrative management of permanent and temporary staff, the financial management of all allocated credits and the monitoring of research contracts.

Composition :

Séminaires à venir

Vendredi 20 septembre 2019, 14h00
Atelier, Paris
Challenging a Newtonian prediction through Gaia wide binaries
Xavier HERNANDEZ
UNAM, Mexico
résumé :
Under Newtonian dynamics, the relative motion of the components of a binary star should follow a Keplerian scaling with separation. Once orientation effects and a distribution of ellipticities are accounted for, dynamical evolution can be modelled to include the effects of Galactic tides and stellar mass perturbers. This furnishes a prediction for the relative velocity between the components of a binary and their projected separation. After reviewing recent work evidencing the existence of a critical acceleration scale in Elliptical Galaxies and Globular Clusters, I will show new results showing such a phenomenology in Gaia wide binaries using the latest and most accurate astrometry available. The results are consistent with the Newtonian prediction for projected separations below 7000 AU, but inconsistent with it at larger separations, where accelerations are expected to be lower than the critical a0 value of MONDian gravity. This result challenges Newtonian gravity at low accelerations and shows clearly the appearance of gravitational anomalies of the type usually attributed to dark matter at galactic scales, now at much smaller stellar scales.


 
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